Fuel cell system

Abstract

A fuel cell system which prevents a reduction in catalyst activity, wherein at least one of the anode catalyst layer and the cathode catalyst layer includes a core-shell type catalyst particle having a core portion including a core metallic material and a shell portion covering the core portion and including a shell metallic material; and wherein the fuel cell system has: a means for storing an initial value of a ratio of the core metallic material to a surface area of the core-shell type catalyst particle, and a means for determining whether or not the ratio of the core metallic material to the surface area of the core-shell type catalyst particle is increased at a predetermined stage, compared to the initial value.

1 . A fuel cell system comprising a fuel cell which comprises single fuel cells, each of which comprises a membrane electrode assembly in which an anode electrode comprising an anode catalyst layer is provided on one surface of a polymer electrolyte membrane, while a cathode electrode comprising a cathode catalyst layer is provided on the other surface of the polymer electrolyte membrane,
 wherein at least one of the anode catalyst layer and the cathode catalyst layer comprises a core-shell type catalyst particle having a core portion comprising a core metallic material and a shell portion covering the core portion and comprising a shell metallic material; and   wherein the fuel cell system has:   a means for storing an initial value of a ratio of the core metallic material to a surface area of the core-shell type catalyst particle, and   a means for determining whether or not the ratio of the core metallic material to the surface area of the core-shell type catalyst particle is increased at a predetermined stage, compared to the initial value.   
     
     
         2 . The fuel cell system according to  claim 1 , wherein the determining means makes a determination based on a detection result that indicates gas desorption from the core-shell type catalyst particle and/or a detection result of the gas desorbed. 
     
     
         3 . The fuel cell system according to  claim 1 , wherein the determining means makes a determination based on the ratio of the core metallic material to the surface area of the core-shell type catalyst particle, which is obtained by comparing a current peak at a potential at which first gas that is supplied to at least the membrane electrode assembly and/or an oxide of the first gas is desorbed from the core metallic material, with a current peak at a potential at which the first gas and/or oxide thereof is desorbed from the shell metallic material. 
     
     
         4 . The fuel cell system according to  claim 3 , wherein the first gas is carbon monoxide. 
     
     
         5 . The fuel cell system according to  claim 1 , wherein the core metallic material is a metallic material which absorbs second gas that is supplied to at least the membrane electrode assembly, and the determining means makes a determination based on the presence of a current peak at a potential at which the second gas is released from the core metallic material. 
     
     
         6 . The fuel cell system according to  claim 5 , wherein the determining means further makes a determination based on an integrated value of the current peak. 
     
     
         7 . The fuel cell system according to  claim 5 , wherein the second gas is hydrogen gas. 
     
     
         8 . The fuel cell system according to  claim 5 , wherein oxidant gas is supplied to the cathode electrode, and an amount of the oxidant gas supplied upon executing the determining means is lower than that of oxidant gas supplied in normal operation. 
     
     
         9 . The fuel cell system according to  claim 5 , wherein a voltage higher than a standard electrode potential of the core metallic material is applied to the fuel cell when it is determined by the determining means that the ratio of the core metallic material to the surface area of the core-shell type catalyst particle is increased compared to the initial value. 
     
     
         10 . The fuel cell system according to  claim 9 , wherein the standard electrode potential of the core metallic material is less than a standard electrode potential of the shell metallic material, and the voltage applied to the fuel cell is within the range from the standard electrode potential of the core metallic material to less than the standard electrode potential of the shell metallic material. 
     
     
         11 . The fuel cell system according to  claim 9 , wherein, when a voltage higher than the standard electrode potential of the core metallic material is applied to the fuel cell, a concentration of gas which is supplied to one of the anode electrode and the cathode electrode is increased higher than that of the same which is generally supplied; or a concentration of gas which is supplied to the other electrode is decreased lower than that of the same which is generally supplied; or the concentrations of the gasses are controlled at the same time. 
     
     
         12 . The fuel cell system according to  claim 9 , wherein the core-shell type catalyst particles are contained only in the cathode catalyst layer, and when a voltage higher than the standard electrode potential of the core metallic material is applied to the fuel cell, a concentration of oxidant gas which is supplied to the cathode electrode is increased higher than that of the same which is generally supplied; or a concentration of fuel gas which is supplied to the anode electrode is decreased lower than that of the same which is generally supplied; or the concentrations of the gasses are controlled at the same time. 
     
     
         13 . The fuel cell system according to  claim 1 , wherein the system has a means for detecting gas produced in the cathode electrode, and the determining means makes a determination based on a detection result obtained by the detecting means. 
     
     
         14 . The fuel cell system according to  claim 13 , wherein the cathode catalyst layer of the cathode electrode comprises a carbon carrier as a catalyst carrier, and the detecting means detects carbon dioxide.